Method of stabilizing acetylene polymers



Oct. 25, 1966 RYUICHI KOBAYASHI 3,

METHOD OF STABILIZING ACETYLENE POLYMERS Filed May 9, 1963 United States Patent 3,281,486 METHOD OF STABILIZING ACETYLENE POLYMERS Rynichi Kobayashi, Nishiknbiki-gun, Japan, assignor t0 Denki Kagaku Kogyo Kabushiki Kaisha, Tokyo, Japan, a corporation of Japan Filed May 9, 1963, Ser. No. 279,224 Claims priority, application Japan, Oct. 5, 1962, 37/ 43,050; Dec. 1, 1962, 37/53:,457 7 Claims. (Cl. 260-678) The present invention relates to a method of stabilization of acetylene polymers formed as by-products in case of the synthesis of chloroprene, and more particularly to a method of treating divinyl acetylene with safety.

The object of the invention is to effectively stabilize acetylene polymers by preventing dangerous explosion with an addition of a small quantity of inexpensive stabilizer and by simple manner.

The single figure in the accompanying drawing is a schematic representation of one system of apparatus which may be used in carrying out the invention.

In the process of synthesizing monovinyl acetylene from acetylene, the trimer to tetramer of acetylene are byproduced and more particularly, the divinyl acetylene which is a trimer is unavoidably produced as a by-product. Divinyl acetylene absorbs even a very small quantity of oxygen to produce peroxide easily and polymerizes, while the polymer of divinyl acetylene peroxide has remarkable explosive nature and causes explosive decomposition by slight friction or impact as is well known. Further difliculties of divinyl acetylene is that it passes through the gelatinized state from the liquid state in the polymerization step and solidifies to hard and brittle resinous substances and once gelated it becomes insoluble to all solvents, more particularly, in such a place that divinyl acetylene condenses and deposits from vapor phase the polymer of divinyl acetylene containing peroxide is liable to be produced on the wall of an apparatus and adheres thereto.

The explosivity of the vinyl acetylene polymers becomes sensitive from when it is gelated even before it does not become resinous state.

As the method of suppressing the formation of such strong explosive divinyl acetylene polymer it has heretofore been proposed to protect the inside of the system from air and substitute with inert gas such as nitrogen gas atmosphere or to use reducing stabilizer such as hydroquinone or thiodiphenyl amine, yet such means are not effective as the perfect protection, i.e., even a very small quantity of oxygen contained in nitrogen is absorbed by the divinyl acetylene and forms explosive polymer during a long period.

Moreover, even though the stabilizer serves as a retardant it only delays the polymerization time as illustrated in the examples described later and the explosive nature of the divinyl acetylene polymer once produced has almost no difference from that of the divinyl acetylene polymers containing no stabilizer.

Next, the method of diluting with an ordinary solvent such as methanol acetone, toluene, kerosene and the like it only somewhat delays the polymerization time even when used a large quantity of such solvent with respect to the divinyl acetylene and it is impossible to extinguish the explosive nature of divinyl acetylene polymers. For instance, in case of a solution of 80% of acetone and of divinyl acetylene the polymerization time becomes about 3 times longer but the explosive nature of the produced gel does not cause large difference. Furthermore, a great disadvantage of this process is that a very expensive solvent should be used for a large quantity relative to the divinyl acetylene so that when using such process it is very uneconomical.

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After various investigations about effective method of stabilizing divinyl acetylene the inventor has found that the addition of a small amount of heavy oil such as Bunker C-fuel oil (No. 6 fuel oil, ASTM D396-6lT) or a heavy oily composition such as asphalt, pitch and coal tar enables to prevent the polymerization of divinyl acetylene for a long period and also divinyl acetylene polymers produced under the presence of heavy oil absorbs less oxygen and explosive nature due to the impact or collision is lessened to a considerable degree.

The term heavy oil in the specification and claim includes all common heavy fuel oils, crude oils, and heavy oily compositions such as asphalt, pitch and coal tar.

The specialty of the method of stabilizing divinyl acetylene by the addition of heavy oil is that the addition of a very small quantity of heavy oil increases the stability of divinyl acetylene considerably. For instance, the addition of 2 to 20 weight parts of heavy oil with respect to parts of divinyl acetylene perfectly suppresses the polymerization of divinyl acetylene for a long period more than 100 days and moreover the peroxide in the divinyl acetylene polymers is very little and the stability can be increased to such an extent that the explosive property due to collision does not occur firing even by hammering. Moreover, since divinyl acetylene and heavy oil dissolve well each other heavy oil can be perfectly dissolved by feeding a small quantity of heavy oil from the upper part of liquid phase of stationary divinyl acetylene to become uniform solution and induces no local production of dangerous polymer.

By what mechanism heavy oil contributes to the stabilization of divinyl acetylene and what composition of heavy oil mainly acts to stabilization are not still clear, but No. 5 fuel oils (ASTM D39661T) as well as asphalt, pitch and coal tar are ascertained to be effective and also the crude oil containing heavy oil is effective to increase the stability of divinyl acetylene similar to heavy oil. Accordingly, by adding a small quantity of heavy oil which is comparatively low price the stability of divinyl acetylene can be improved compared with the method of adding a conventional reducing stabilizer so that economical and stable operation can be attained.

Further on the wall of an apparatus in the vapor phase of the portion where divinyl acetylene exists pure divinyl acetylene not containing stabilizer is liable to condense on the wall and if it makes contact with a very small quantity of oxygen dangerous and explosive product may be formed so that in order to prevent such formation a small drop of heavy oil is spread on the wall, then the heavy oil is uniformly applied to the wall as thin film enabling to prevent the adhesion of divinyl acetylene polymers on the wall surface by the condensation of gaseous divinyl acetylene.

By carrying out the addition of heavy oil as above described the very dangerous divinyl acetylene polymer does not adhere during the refining process of monovinyl acetylene so that safe and stable operation can be continued for a long duration.

Now the invention will be described with reference to the following examples.

Example 1 The quantity of oxygen absorbed by the divinyl acetylene refined 'by reduced pressure distillation under nitrogen current and sensitivity to impact of divinyl acetylene polymer polymerized While forming peroxide were measured.

3.00 g. of pure divinyl acetylene were put in a Pyrex glass tube and made contact with air while continuously vibrating and the absorbed quantity of oxygen in air was measured quantitatively. At room temperature it gelated in 13 days and the absorbed quantity of oxygen was 115.7

cc. (normal state). This shows that 0.134 mol of oxygen based on 1 mol of divinyl acetylene has reacted to peroxide, This divinyl acetylene polymer violently ignites by a slight impact so that it is very dangerous substance and the sensitivity to impact was measured to be less than 0.008 kg.-m.

Next, in order to examine the effect of the stabilizer the test was made by adding 0.0005 weight part of the stabilizer such as hydroquinone, thiodiphenyl amine, ptert.-butyl catechol, phenyl-B-naphthylamine to 1 part of divinyl acetylene. The absorption speed of oxygen was delayed and the polymerization time was extended to 40 to 60 days, yet the content of oxygen in the polymer was 0.1 to 0.15 mol per 1 mol of divinyl acetylene and the sensitivity to impact was almost to the same extent as no stabilizer was added to divinyl acetylene.

The effect of adding solvent was tested by the similar weight parts of divinyl acetylene and the mixture was contacted with air, then the polymerization time was considerably delayed and took 85 days before gelated and the quantity of oxygen absorbed before gelated was 0.087 mol to 1 mol of the sample. The sensitivity to impact of the polymer was measured to be 280 kg.-m. so that the stability increased considerably if compared with the above described experimental results.

Next, when 10 weight parts of Bunker C-fuel oil were added to 90 weight parts of divinyl acetylene the stability increased further and took 113 days before it gelated and the absorbed quantity of oxygen before it gelated was 0.061 mol to 1 mol of the sample and the sensitivity to impact was 4.50 kg.-m. and the ignition ability of the polymer was reduced considerably.

In order to describe the detail of examples the experimental data are shown in Table 1.

TABLE 1 Sample Polymer Sensitivity to Absorbed Quantity 0 impact DVA, weight Addition quantity of stabilizer, Weight Gelation (kg-m.)

percent Solvent, weight percent G./sample g. (g.) time (day) N.T.P., M01 ratio vs.

0.0. sample 3.00 13 115.7 0.134 0.008 Hydroquinone 0.0005. 3.06 54 128 .6 0.140 0.008 Thiodiphenylamine 0.0005. 3 .02 58 75 .3 0 .080 0.008 Phenyl-fi-naphthylamine 0.0005. 3 .03 39 84.9 0.097 0.008 t-Butyl catechol 0.0005. 3 .13 45 123 .5 0.138 0.008 Acetone 80. 3 .15 40 133 .5 0.115 0.049 ..d 3.10 68 35.7 0.031 0.050 Toluene 50 3 .22 51 96 .9 0 .113 0.023 Toluene 10 Hydroquinone 0 0020 3.21 65 67.1 0.074 0.008 Bunker C-fuel oil, 3.01 65 75.5 1 0.087 2.80 90 Bunker C-luel oil, 10.. 3.02 113 53.2 1 0.001 4.50

1 The molecular weight of the sample was calculated based on the molecular weight of DVA. Divinyl acetylene is abridged as DVA.

manner and found that the solut1on containing weight Example 2 parts of divinyl acetylene and 80 weight parts of acetone gelated in days and the absorbing quantity of oxygen was 0.115 mol to 1 mol of divinyl acetylene and the sensitivity to impact was 0.049 kg.-m. The solution containing weight parts of divinyl acetylene and 50 weight parts of toluene gelated in 51 days and the absorbing quan- The polymerization time, absorbed quantity of oxygen and sensitivity to impact of divinyl acetylene at 50 C. were measured in the similar manner to Example 1. The obtained results are described as a whole in Table 2. In this case it will be apparent that similar to the case of room temperature divinyl acetylene is perfectly treated r tlty of oxygen was 0.113 mol to 1 mol of sample and the 4 by adding heavy 011.

TABLE 2 Sample Polymer Absorbed quantity 0; Sensitivity to DVA, welght Gelation impact (kg.-m.)

percent Solvent, weight percent Quantity of stabilizer GJsample g. Weight time (day) (g.) N.'I.P., Mol ratio 0.0. vs. sample 3 10 7 42. 9 0. 048 0. 075 Hydroqulnone, 0.0010. 3.06 10 37. 5 0. 043 0. 143 Acetone, 80. 3. 06 17 64. 6 0. 058 0. 086 .....do- Hydroqumone, 0.0010 3.03 28 31. 9 0.029 0.002 Toluene, 50- l 3. 24 10 85. 4 0. 099 0. 050 Bunker C-fuel oil, 2 3. 02 45 32. 0 1 0. 037 3. Bunker C-luel Oil, 10 3. 02 92 29. 2 1 0. 034 5. 00

1 Same as in Table. '1. sensitivity to impact was 0.023 kg.-m. By adding stabilizer Example 3 to these solutions the polymerization time was somewhat extended but no special effect could be recognized.

From the above experiments, it has been ascertained that by adding a conventional stabilizer and a solvent to divinyl acetylene the polymerization time was extended but it was impossible to suppress the dangerous property of vinyl acetylene polymers once gelated..

In this respect, measurement had been made for the quantity of oxygen in air to be absorbed by divinyl acetylene, polymerization time and sensitivity to impact thereof when Bunker C-fuel oil dissolves in divinyl acetylene was added by the similar manner as above described.

In the process of eliminating water soluble solvent such as acetone, methanol by extracting the mixed solution of divinyl acetylene-acetone for example obtained in case of manufacturing ehloroprene with water (using the apparatus as set forth in the accompanying drawing), heavy oil from tube 3 was charged into the tower 1 through a preheater 4 and inert gas (such as nitrogen gas) from tube 5 was forced through nozzle 2 into the tower to spray heavy oil over a wide range and the inner wall of the top of the tower was kept always wetted with fine drops of heavy oil, 10 weight parts of said heavy oil being added 2 weight parts of Bunker C-fuel oil were added to 98 to 100 parts of divinyl acetylene as a whole. The solvent was extracted into water layer 8 in the tower 1 and the divinyl acetylene layer 9 containing heavy oil was exhausted out of the tower and inert gas was discharged from pipe 6 through water sealed apparatus 7.

By adopting such a method divinyl acetylene was stabilized and safe and stable operation can be carried out for 200 days. After the operation was stopped and the apparatus was disassembled it was found that the inner wall of the top of the tower was covered with uniform film of heavy oil and no formation of explosive divinyl acetylene polymer was recognized to adhere to the inner wall of the tower.

On the contrary, the absorption speed of oxygen and the polymerization time under the existence of asphalt, pitch, coal tar and the like substances became very slow and it took more than 1 00 days before it was gelated and the quantity of oxygen absorbed before gelation was less than 70 cc. for the sample of 3 g.

The sensitivity to impact of these polymers was 3.0 to 5.0 kg.-m. so that the explosive nature of the polymer had been considerably reduced if compared with the above mentioned results.

In order to describe the example, the experimental data are shown in Table 3.

TABLE 3 Sample Polymer Sensitivity Absorbed quantity O to impact DVA, weight Heavy oily composition, Antioxidant, Weight Gelati0n (kg-m.)

percent weight percent g./l. (g.) time (day) N.T.P., Mol ratio c.e. vs. sample 3. 00 13 115. 7 0.134 0. 008 Hydroquinone, O.5.---... 3.06 54 128. 6 0.146 0. 008 Thiodipheuylamine, 0.5.. 3. 02 58 75. 3 O. 087 0. 008 Bunker C-fuel oil, 3.02 113 53.2 1 0.061 4. 50 Asphalt, 10 3. 10 124 46. 7 1 0. 065 5. 00 Coal tar, 10.. 3. 10 115 57. 4 1 0. 082 3. 50 Pitch, 10.... 3.00 110 49. 8 1 0.071 3.

1 Same as in Table 1.

Example 4 Example 5 The quantity of oxygen absorbed by the divinyl acetylene refined by reduced pressure distillation under nitrogen current and sensitivity to impact of divinyl acetylene polymer polymerized while forming peroxide were measured for the case with or without a conventional antioxidant and when heavy oil composition such as asphalt, pitch and coal tar is added.

The gelation time, absorbed quantity of oxygen and sensitivity to impact of divinyl acetylene at C. were measured in the similar manner to Example 4. The obtained results are described as a whole in Table 4. In this case it will be apparent that similar to the case of room temperature divinyl acetylene is safely treated by adding heavy oil.

TABLE 4 Sample Polymer Absorbed quantity O Sensitivity DVA, weight Heavy oily composition, Antioxlildant, W2eig)ht nieltztflron) tpknnpagt 'e' ht ereent g. e ay g.-m. percent 1g p g N.T.P., M01 ratio 0.0. vsv sample 3. 10 7 42. 9 0. 048 O. 075 Hydroqu on 1.0.... 3. 06 10 37. 5 0. 043 O. 143 3. 02 92 29. 2 1 O 034 5. O0 3. 08 104 23.9 1 0. 033 5. 00 3. 08 98 32. 2 1 0, 045 5. 00 90 Pitch, 10.. 06 93 30. 2 1 043 4. 5O

1 Same as in Table 1.

3.00 g. of pure divinyl acetylene Without antioxidant What I claim is:

were put in a Pyrex glass tube and made cont-act with air while continuously vibrating and the absorbed quantity of oxygen in air was measured quantitatively. At room temperature it gelated in 13 days and the absorbed quantity of oxygen was 115.7 cc. (normal state). This shows that 0.134 mol of oxygen based on 1 mol of divinyl acetylene has reacted to peroxide. This divinyl acetylene polymer violently ignites by a small shock so that it is very dangerous substance and the sensitivity to impact was measured to be less than 0.008 kg.-m.

Next, the absorption speed of oxygen under the existence of antioxidant such as hydroquinone became slow and the polymerization time increased to 54 days and the quantity of oxygen absorbed was 128.6 cc. and the sensitivity to impact was almost same as that when no antioxidant existed. Accordingly, by the addition of a conventional antioxidant to divinyl acetylene the polymerization time is extended, but the dangerous nature of divinyl acetylene polymer once formed is impossible to be suppressed.

1. A method of stabilizing divinylaeetylene against the formation of explosive byproducts consisting essentially of adding to the divinylacetylene a minor amount by weight of a heavy oil or a substance containing said heavy oil.

2. A method of stabilizing divinylacetylene according to claim 1 wherein said heavy oil or a substance containing said heavy oil is sprayed onto the Walls of a vessel containing divinylacetylene in order to cover the wall surfaces With a film of said heavy oil and said heavy oil is simultaneously added to the liquid divinylacetylene in the vessel.

3. A method according to claim 1 wherein said heavy oil is Bunker-C fuel oil.

4. A method according to claim 1 wherein said heavy oil is selected from the group consisting of asphalt, pitch I and coal tar.

7 6. A method according to claim '1 wherein said heavy oil is added in from 2 to 20 parts by Weight based on the weight of divinylacetylene.

7. A method of stabilizing divinylacetylene against the formation of explosive byproducts consisting essentially of adding to the divinylacetylene from 2 to 20 parts by Weight of a heavy oil selected from the group consisting of a fuel oil having a kinematic viscosity of more than 30 centistokes at 100 F., asphalt, pitch and coal tar.

References Cited by the Examiner UNITED STATES PATENTS 2,934,575 4/1960 Apotheker 260-678 ALPHONSO D. SULLIVAN, Primary Examiner. 

1. A METHOD OF STBLIZING DIVINYLACETYLENE AGAINST THE FORMATION OF EXPLOSIVE BYPRODUCTS CONSISTING ESSENTIALLY OF ADDING TO THE DIVINYLACETYLENE A MINOR AMOUNT BY WEIGHT OF A HEAVY OIL OR A SUBSTANCE CONTAINING SAID HEAVY OIL. 